in;'.  f 


Issued  September  10, 191'i. 

HAWAII  AGRICULTURAL  EXPERIMENT  STATION, 

E.  V.  WILCOX,  Special  Agent  in  Charge. 


Bulletin  No.  28. 


THE  EFFECT  OF  MANGANESE  ON 
PINEAPPLE  PLANTS 

AND 

THE  RIPENING  OF  THE 


PINEAPPLE  FRUITSl 


BY 

E.  V.  WILCOX, 

Special  Agent  in  Charge 

AND 

W.  P.  KELLEY, 

Chemist. 


UNDER  THE  SUPERVISION'  OF 
OFFICE  OF  EXPERIMENT  STA 

U.   8.   DEPARTMENT  OF  AGRICTJLTU 


WASHINGTON: 
GOVERNMENT   PRINTING   OFFICE. 

i:M2. 


Issued  September  10,  1912. 

HAWAII  AGRICULTURAL  EXPERIMENT  STATION, 

E.  V.  WILCOX,  Special  Agent  in  Charge. 


Bulletin  No.  28. 


THE  EFFECT  OF  MANGANESE  ON 
PINEAPPLE  PLANTS 

AND 

THE  RIPENING  OF  THE 
PINEAPPLE  FRUIT. 


BY 

E.  V.  WILCOX, 

Special  Agent  in  Charge, 

AND 

W.  P.  KELLEY, 

Chemist. 


UNDER  THE  SUPERVISION  OF 
OFFICE  OF  EXPERIMENT  STATIONS, 

U.   9.    DEPARTMENT  OF  AGRICULTURE. 


WASHINGTON: 

GOVERNMENT   PRINTING   OFFICE. 

1912. 


HAWAII  AGRICULTURAL  EXPERIMENT  STATION,  HONOLULU. 

[Under  the  supervision  of  A.  C.  True,  Director  of  the  Office  of  Experiment 
Stations,  United  States  Department  of  Agriculture.] 

Walter  H.  Evans,  Chief  of  Division  of  Insular  Stations,  Office  of  Experiment 

Stations. 

STATION  STAFF. 

E.  V.  Wilcox,  Special  Agent  in  Charge. 
J.  Edgar  Higgins,  Horticulturist. 
W.  P.  Kellev,  Chemist. 

C.  K.  McClelland,  Agronomist. 

D.  T.  Fullaway,  Entomologist. 

W.  T.  McGeorge,  Assistant  Chemist. 
Alice  R.  Thompson,  Assistant  Chemist. 
C.  J.  Hunn,  Assistant  Horticulturist. 
V.  S.  Holt,  Assistant  in  Horticulture. 
C.  A.  Sahr,  Assistant  in  Agronomy. 

(2) 
[Bull.  28] 


LETTER  OF  TRANSMITTAL 


Honolulu,  Hawaii,  May  1,  1912. 
Sir:  I  have  the  honor  to  submit  herewith  and  recommend  for 
publication,  as  Bulletin  Xo.  28  of  the  Hawaii  Agricultural  Experi- 
ment Station,  a  paper  on  the  Effect  of  Manganese  on  Pineapple 
Plants,  and  the  Ripening  of  Pineapple  Fruit,  prepared  jointly  by 
myself  and  Mr.  W.  P.  Kelley,  chemist.  Chemical  investigation  on 
the  cause  of  yellowing  of  pineapples  on  certain  soils  and  on  the 
ripening  of  the  pineapple  fruits  has  been  carried  on  for  the  past 
three  years,  and  some  of  the  important  results  of  this  investigation 
are  stated  in  this  paper.  A  microscopic  study  was  made  of  all  the 
different  parts  of  pineapples  for  the  purpose  of  learning  the  struc- 
tural changes  produced  by  the  presence  of  large  quantities  of  man- 
ganese in  the  soil  and  the  morphological  changes  which  occur  in  the 
ripening  of  the  fruit.  The  anatomical  and  chemical  findings  are  in 
rather  striking  harmony.  The  practical  bearing  of  these  investiga- 
tions should  be  of  importance  in  the  further  development  of  the 
pineapple  industry. 

Respectfully,  E.  V.  Wilcox, 

Special  Agent  in  Charge. 
Dr.  A.  C.  True, 

Director  Office  of  Experiment  Stations, 

V.  S.  Department  of  Agriculture,  'Washington,  D.  C. 

Publication  recommended. 
A.  C.  True,  Director. 

Publication  authorized. 

Ja^ies  "Wilson,  Secretary  of  Agriculture. 

(3) 

[Bull.  28] 


CONTENTS. 


Page. 

The  effect  of  manganese  on  pineapple  plants 7 

Introduction 7 

Pineapple  roots 7 

Leaves 8 

Oxalate  of  lime 11 

Other  visible  effects  of  manganese 11 

The  chemistry  of  the  pineapple  plant 12 

The  composition  of  the  pineapple  plant  as  affected  by  manganese 13 

The  ripening  of  the  pineapple  fruit 14 

The  chemistry  of  ripening 16 

Summary 19 


ILLUSTRATIONS. 


Page. 

Plate  I.  Structure  of  pineapple  leaf  showing  effect  of  manganese 8 

II .  Cells  from  pineapple  leaves  and  fruits 8 

(5) 
[Bull.  28] 


THE  EFFECT  OF  MANGANESE  ON  PINEAPPLE  PLANTS,  AND 
THE  RIPENING  OF  THE  PINEAPPLE  FRUIT. 


THE  EFFECT  OF  MANGANESE  ON  PINEAPPLE  PLANTS. 
INTRODUCTION. 

The  pineapple  belongs  to  the  family  Bromeliacea?,  several  species 
of  which  are  of  epiphytic  habit.  With  the  exception  of  the  black 
moss  of  the  South  which,  as  its  name  indicates,  has  a  moss-like  habit 
of  growth  and  small  terete  branches,  the  members  of  this  family 
which  we  have  been  able  to  examine  show  very  similar  structure  and 
arrangement  of  the  cellular  tissue  of  the  leaves.  The  pineapple  pre- 
sents certain  peculiar  habits  of  growth  which  constantly  remind  one 
of  the  fact  that  it  belongs  to  a  family  of  plants  in  which  a  number  of 
epiphytic  species  occur.  The  family  as  a  whole  occurs  principally  in 
tropical  and  subtropical  climates  and  exhibits  a  power  of  adaptation 
to  a  wide  range  of  conditions  of  soil  and  rainfall. 

The  studies  reported  in  this  bulletin  were  undertaken  jointly  as  a 
continuation  of  the  work  reported  by  this  station  regarding  the  effect 
of  manganese  on  pineapples,  and  also  regarding  some  of  the  points 
which  have  been  observed  in  the  chemical  composition  of  pineapple 
fruits  in  different  stages  of  development.1  It  will  be  noticed  in  study- 
ing the  results  which  we  have  obtained  that  the  anatomical  and 
chemical  findings  are  in  remarkable  harmony  and  that  they  mutually 
assist  in  explaining  each  other. 

PINEAPPLE   ROOTS. 

One  of  the  points  which  is  likely  to  appear  most  striking  in  the 
study  of  pineapples  in  the  field  is  the  great  variation  in  the  root 
structures.  Under  favorable  conditions  the  roots  may  be  several  feet 
in  length  and  may  quite  fully  occupy  the  soil  in  all  directions  from 
the  base  of  the  plant.  In  pulling  up  apparently  vigorous  plants, 
however,  many  will  be  found  to  have  almost  no  root  system,  although 
the  aerial  portion  of  the  plant  appears  to  be  as  vigorous  as  those 
which  possess  a  well-developed  set  of  roots.  Moreover,  it  is  also  a 
striking  fact  that  even  on  many  of  the  most  healthy  plants  the  roots 
may  be  nearly  all  dead  and  in  process  of  decay,  with  only  here  and 

1  Hawaii  gta.  Bui.  26  ;  Press  Bui.  23^  Rpt.  1909,  pp.  58-63;  Rpt.  1910,  pp.  41^3,  45-50. 

(7) 

[Bull.  28] 


8 

there  a  living  root  covered  near  its  growing  tip  with  root  hairs.  In 
the  zone  of  the  root  where  the  root  hairs  occur  these  structures  are 
remarkably  abundant,  the  large  majority  of  the  epidermal  cells  of 
the  root  being  developed  into  hair  structures.  It  is  a  difficult  matter, 
therefore,  to  wash  the  soil  away  from  these  portions  of  the  roots 
without  tearing  off  the  root  hairs.  It  is  impossible  to  determine  with 
certainty  the  causes  which  bring  about  the  great  variation  in  the 
length  and  number  of  living  roots  on  plants  which  seem  to  be  quite 
vigorous  and  on  normal  soils.  The  proper  development  of  the  root 
system,  however,  seems  to  depend  largely  upon  suitable  physical  con- 
ditions in  the  soil.  Where  drainage  is  poor  and  where  the  soil 
becomes  packed  or  puddled  below  the  depth  of  cultivation,  it  is 
impossible  for  the  roots  to  penetrate  and  develop  as  they  otherwise 
might  do. 

In  general  it  may  be  said  that  the  root  system  of  pineapples  grow- 
ing on  highly  manga niferous  soils  is  rather  less  extensive  than  that 
observed  on  normal  soils.  The  number  of  small  fibrous  branches  on 
the  main  roots  is  much  reduced  in  manganiferous  soils.  One  of  the 
most  striking  effects  of  a  high  percentage  of  manganese  in  the  soil  is 
observed  in  the  root  tips,  which  quite  generally  show  rounded  swollen 
ends  rather  than  the  pointed  tips  with  rootcaps,  such  as  occur  in  nor- 
mal soils.  These  swollen  root  tips  are  almost  invariably  dead  or 
dying  and  usually  are  found  in  process  of  decay.  It  is  obvious  that 
they  have  in  all  cases  ceased  growing.  In  fact,  growth  is  impossible 
after  the  swelling  occurs,  since  the  roots  are  then  unable  to  penetrate 
farther  into  the  soil.  In  the  woody  tissue  and  in  the  cells  imme- 
diately under  the  epidermis  of  roots  growing  in  manganiferous  soil 
there  is  a  slightly  greater  tendency  toward  browning  of  the  cell  walls 
than  is  the  case  in  normal  soils. 

LEAVES. 

The  leaves  of  the  pineapple  and  other  members  of  the  same  family 
with  similar  habits  of  growth  are  attached  to  the  short  stems  of  the 
plant  close  together  and  spread  at  an  angle  of  45°,  more  or  less,  from 
the  axis  of  the  plant.  The  edges  of  the  leaves  are  curved  upward, 
so  that  a  cross  section  of  a  leaf  is  approximately  a  semicircle. 

In  the  normal  pineapple  plant  the  upper  surface  of  the  leaf  shows 
a  conspicuous  red  color,  which  is  confined  to  the  central  third  of  the 
leaf  surface.  The  upward  curving  of  the  edges  of  the  leaf  naturally 
divides  the  upper  surface  of  the  leaf  into  three  nearly  equal  portions, 
two  being  upright,  one  on  either  side,  and  the  third  portion  lying  at 
the  bottom  of  the  trough.  This  central  or  lower  third  receives  the 
sunlight  to  a  much  greater  degree  than  the  sides  of  the  leaf,  and  the 
development  of  a  red  coloring  matter  in  the  lower  third  seems  to  be 

[Bull.  23] 


jl.  28,  Hawaii  Agr.  Expt.  Station. 


Pl-ATF    I. 


J. 


■v»fe. 


5a  rH?  K^I/iMK!**' 


I 


ti 


I    i* 


c 


*'■■ 


Str_  f,  showing  Effect  of  Manganese. 

- 


Jul.  28,  Hawaii   Agr.  Ex;  I 


Plate 


Cells  ff  ple  leaves  and  Fru 

..in  highlj   n 

1    rrom  pulp  of  ripe  pineapple  fruit. 


directly  connected  with  this  fact.  It  apparently  forms  a  screen 
which  protects  the  underlying  chlorophyll  from  the  intense  action  of 
the  tropical  sun.  This  hypothesis  is  home  out  by  the  arrangement  of 
the  chlorophyll  in  the  leaves  of  pineapples  and  related  species  of  the 
same  family,  as  will  be  presently  shown. 

One  of  the  peculiar  features  of  the  pineapple  leaf  is  the  apparent 
absence  oi'  stomata.  Hundreds  of  sections  were  made  from  pine- 
apple  leaves  and  examined  under  the  microscope,  and  portions  of  the 
epidermis  of  the  upper  and  under  sides  of  the  leaves  were  carefully 
examined  without  finding  any  true  stomata.  There  are  in  some 
parts  of  the  leaves  pits  in  the  epidermis  in  which  much-branched 
scale-like  trichomes  are  attached.  These  structures  are  particularly 
numerous  on  the  under  side  of  the  leaf  near  the  base.  The  trichomes 
in  question  are  supposed  to  be  connected  with  the  absorption  o| 
water. 

Running  through  the  leaves  parallel  to  the  strands  of  fibrovascular 
tissue  are  strands  of  branched  or  stellate  cells,  which  show  large 
intercellular  spaces  between  their  branches.  These  strands  lie  directly 
over  the  pits  in  the  epidermis  of  the  lower  side  of  the  leaf  and 
seem  to  be  connected  with  transpiration  and  the  absorption  of  gases. 
It  would  appear  that  the  respiratory  system  of  the  pineapple  is 
abortive,  for  when  the  leaves  of  Bromelia  are  studied  the  develop- 
ment  of  the  strands  of  branched  cells  and  the  stomata  is  very  con- 
spicuous.  In  this  genus  there  are  numerous  small  tubular  masses 
of  branched  cells  which  extend  from  the  general  strands  of  this 
tissue  to  the  epidermis  of  the  lower  side  of  the  leaf  and  are  directly 
connected  with  the  stomata,  which  are  arranged  very  close  together 
in  parallel  furrows  which  alternate  with  ridges  on  the  lower  surface 
of  the  leaf.  In  the  pineapple,  on  the  other  hand,  there  are  no  spe* 
cially  modified  cells  connecting  the  strands  of  branched  cells  with 
the  epidermis.  In  Greigia,  another  genus  of  this  family,  no  branched 
cells  occur  in  the  leaves.  The  chlorophyll-bearing  tissue  in  this 
genus  is  a  very  thin  layer  on  the  lower  surface  of  the  leaf,  and  the 
respiratory  processes  appear  to  go  on  without  the  assistance  of  the 
stellate  cells. 

In  cross  sections  of  normal  pineapple  leaves  it  is  at  once  noticed 
that  from  one-fifth  to  two-fifths  of  the  thickness  of  the  leaf  on  the? 
upper  side  is  composed  of  colorless  tissue  containing  cell  sap  and 
practically  no  other  cell  contents.  This  tissue,  with  the  exception 
of  one  or  two  layers  of  cells  next  to  the  epidermis,  is  concerned  in 
the  movement  and. transportation  of  cell  sap.  Below  the  region  of 
the  palisade  cells  lies  the  spongy  parenchyma,  which  occupies  about 
three-fifths  of  the  thickness  of  the  leaf  of  the  pineapple,  and  through 
which  the  strands  of  fihrovascular  tissue  run  lengthwise  of  the  leaf, 
m°— BnlL  2&— 12 2 


10 

The  chlorophyll  in  the  leaves  of  normal  pineapples  is  nearly  all  con- 
tained in  this  spongy  parenchyma  and  is  therefore  protected  from 
the  direct  sunlight  by  means  of  a  layer  of  cells  next  to  the  epidermis 
containing  a  red  coloring  matter  and  by  a  layer  of  palisade  tissue 
three  or  four  cells  deep.  In  Bromelia  the  palisade  cells  occupy 
about  three-fifths  of  the  thickness  of  the  leaf  and  in  Greigia  about 
four-fifths  of  the  leaf.  The  layer  of  delicate  palisade  cells,  showing 
no  cell  contents  except  cell  sap,  makes  it  a  rather  difficult  matter  to 
obtain  good  free-hand  sections  without  injury  or  disarrangement 
of  the  cell  structure.  The  arrangement  of  the  cell  structures  in  the 
cross  section  of  a  normal  pineapple  leaf  is  shown  in  Plate  I,  A. 

In  contrast  with  the  anatomical  features  of  the  normal  pineapple 
leaf  attention  is  called  to  Plate  I,  B,  which  shows  a  corresponding 
section  of  a  leaf  of  a  pineapple  grown  on  a  highly  manganiferous 
soil.  This  figure  shows  the  destruction  which  has  taken  place  in  the 
chlorophyll  and  the  protoplasmic  bodies  in, general.  A  few  small 
green  granules  are  observed  here  and  there,  but  the  most  of  the 
chlorophyll  bodies  have  been  disintegrated  and  have  disappeared  or 
at  least  lost  their  green  coloring-matter.  In  a  few  instances  it  will  be 
observed  that  the  protoplasmic  bodies  have  become  discolored  with  a 
more  or  less  pronounced  brown.  The  arrangement  of  the  chloroplryll 
bodies  in  the  normal  leaf  is  shown  under  higher  magnification  in  the 
cells  of  spongy  parenchyma  in  Plate  I,  C.  If  the  condition  shown  in 
that  figure  is  compared  with  A,  B,  and  C  of  Plate  II  the  stages  in  the 
disintegration  and  destruction  of  the  chloroplasts  will  be  readily  seen. 
At  first  the  chloroplasts  begin  to  lose  the  regular  form,  and  the  green 
coloring  matter  is  diffused  through  the  protoplasmic  substance  of  the 
cell,  while  the  protoplasmic  bodies  disintegrate  into  smaller  granules 
and  remain  separate  or  are  grouped  together  in  irregular  masses  show- 
ing a  paler  and  paler  green  as  the  effect  of  the  manganese  continues. 
In  the  final  stages  of  the  yellowing  of  the  leaf  every  trace  of  green 
matter  has  disappeared  and  only  small  irregular  granules  of  pale 
protoplasm  are  to  be  seen  in  the  cells  which  previously  carried  normal 
chloroplasts.  The  conspicuous  feature  of  the  effect  of  manganese 
upon  the  growth  of  pineapple  plants  is  the  pronounced  and  peculiar 
yellow  color  of  the  leaves.  Under  the  microscope  the  cause  for  this 
yellowing  is  found  in  the  loss  of  the  green  coloring  matter  and  in  the 
slight  tendencv  toward  the  vellowing  of  the  cell  wall  and  disin- 
tegrated  protoplasmic  substance  under  the  influence  of  manganese. 

In  the  normal  leaf  an  ordinary  iodin  test  shows  the  presence  of 
starch  granules  in  the  protoplasmic  bodies.  Simultaneous  with  the 
etiolation  of  the  chloroplasts  the  iodin  fails  to  show  the  presence  of 
starch.  In  the  later  stages  of  the  yellowing  of  the  leaves  only  occa- 
sional granules  of  starch  are  to  be  found  here  and  there  in  the  dis- 

[Bull.  28] 


11 

integrated  cell  contents  of  the  spongy  parenchyma.  The  amount 
of  starch  which  is  stored  up  in  the  stem  of  the  pineapple,  however, 
is  still  almost,  as  gre^t  in  plants  growing  on  manganese  soils  as  in 
normal  plants. 

The  peculiar  distribution  of  the  chlorophyll  exclusively  at  the 
lower  side  of  the  leaf  seems  to  be  characteristic  of  the  family  Brome- 
liaceaN  so  far  as  we  have  had  opportunity  to  observe.  At  any  rate 
the  chlorophyll  is  regularly  distributed  throughout  the  thickness  of 
the  leaf  or  as  densely  near  the  upper  surface  as  near  the  lower  sur- 
face in  leaves  of  mango,  Croton,  Sapium,  papaya,  Monstera,  sisal, 
Sansevieria,  oleander,  Calophyllum,  Eucalyptus,  Chrysophyllum, 
Agave  americana,  canna,  Peireskia,  banana,  prickly  pear,  CordyUne 
termhialis,  and  vanilla.  In  none  of  these  plants,  except  a  few  in 
the  early  stages  of  growth  of  the  leaves,  is  there  any  pronounced  de- 
velopment of  red  coloring  matter,  which  might  serve  to  protect  the 
chlorophyll,  nor  m  any  of  the  plants  mentioned  is  the  chlorophyll 
restricted  to  the  lower  surface  of  the  leaf.  It  would  seem  from  the 
observations  which  we  have  made  that  the  pineapple  and  closely 
related  species  of  the  same  family  are  particularly  sensitive  plants  in 
this  respect.  The  unusually  rapid  destruction  of  the  chlorophyll 
bodies  and  the  yellowing  of  the  leaves  of  pineapples,  as  compared 
with  other  cultivated  plants  on  manganese  soils,  also  favors  this  view. 

OXALATE  OF  LI3IE. 

Chemical  analyses  Ojl  various  parts  of  the  pineapple  plant  show 
that  there  is  a  much  larger  quantity  of  lime  in  plants  growing  on 
manganese  soils  than  in  those  on  normal  soils.  This  finding  is  partly 
explained  and  further  confirmed  by  the  fact  that  when  examined 
under  the  microscope  all  parts  of  such  plants  are  found  to  contain 
enormously  large  numbers  of  the  needlelike  crystals  of  oxalate  of 
lime.  These  crystals  are  especially  numerous  in  the  fruits,  but  are 
also  relatively  much  more  numerous  in  the  leaves  of  pineapples 
turned  yellow  from  the  effects  of  manganese  than  in  leaves  of  the 
normal  green  plants. 

OTHER  VISIBLE  EFFECTS  OF  MANGANESE. 

However  the  effect  of  manganese  on  pineapples  and  other  plants 
may  be  explained,  it  seems  not  to  be  entirely  due  to  the  increased 
amount  of  manganese  absorbed  by  pineapples  on  highly  manganifer- 
ous  soils,  for  the  amount  of  increase  of  manganese  in  the  ash  is  not 
sufficiently  large  to  permit  such  a  view  to  be  held.  A  thorough 
search  was  made  for  the  possible  visible  appearance  of  manganese  in 
plants  other  than  pineapples.  Minute  concretions  of  manganese  were 
found  on  the  ducts  and  sieve  tubes  in  the  roots  of  mango  and  straw- 
berry.    These   concretions   were   readily   dissolved   by   hydrochloric 

[Bull.  28] 


12 

acid.  The  presence  of  citric  acid  in  pineapples  would  tend  to  keep 
the  manganese  in  solution,  and  this  may  explain  the  fact  that  no 
visible  deposits  of  manganese  could  be  found  in  pineapples. 

In  addition  to  the  brown  color  of  the  protoplasm  referred  to  above, 
it  should  be  mentioned  that  the  roots  of  pineapples  growing  on 
highly  manganiferous  soils  show  a  darker  brown  color  than  in  normal 
plants  and  that  distinct  brown  patches  appear  on  the  upper  surface 
of  the  leaves  of  plants  during  the  later' stages  of  yellowing.  These 
brown  areas  may  be  sunken  or  elevated  and  the  roughness  of  the 
surface  seems  to  be  due  to  the  death  of  the  tissue  underneath  and  the 
consequent  shrinking,  thus  throwing  the  surface  into  folds.  The 
brown  patches  are  perhaps  the  results  of  sun  scald,  which  apparently 
takes  place  more  rapidly  after  the  living  tissues  have  been  injured  by 
manganese  and  the  regulatory  apparatus  is  thereby  destroyed. 

THE    CHEMISTRY    OF    THE   PINEAPPLE    PLANT. 

The  development  of  a  yellow  color  in  the  leaves  of  pineapples  on 
certain  soils  of  Oahu  has  become  a  matter  of  common  observation. 
Investigations  into  the  cause  of  this  phenomenon  have  resulted  in 
establishing  a  direct  relationship  between  the  occurrence  of  manga- 
nese in  the  soil  and  the  yellowing  of  the  pineapples.  In  1909,1 
from  a  preliminary  investigation,  it  was  pointed  out  that  the  degree 
of  yellowing  is  directly  proportional  to  the  amount  of  manganese  in 
the  soil,  and  that  the  manganese  exists  in  the  soil  in  a  state  of  higher 
oxids,  from  which  forms  it  readily  becomes  available  to  the  roots 
of  plants.  It  was  further  shown  by  the  use  of  the  Dyer  method  that 
the  manganese  is  quite  soluble.  Subsequently  it  has  been  pointed 
out  that  the  solubility  of  manganese  in  various  dilute  organic  acids  2 
is  very  pronounced,  and  that  its  solubility  in  distilled  water  in  some 
instances  is  greater  than  that  of  any  other  element  in  the  soil.  It 
was  further  pointed  out  that  the  general  metabolism  of  the  pineapple, 
when  grown  on  manganiferous  soils,  is  considerably  modified.  In 
order  to  throw  more  light  on  this  question,  an  extensive  study  of  the 
chemistry  of  the  pineapple  plant  has  been  undertaken  in  conjunction 
with  the  anatomical  and  physiological  investigations. 

The  results  obtained,  it  is  believed,  will  enable  a  proper  under- 
standing of  certain  peculiarities  already  mentioned  and  afford  a 
more  exact  chemical  basis  for  a  comprehension'  of  the  physiology  of 
the  plant,  and  also  furnish  some  explanation  for  the  peculiarities 
attending  the  presence  of  large  amounts  of  manganese  in  the  soil. 
In  this  study  the  mineral  constituents  of  the  several  parts  of  the 
plant  have  been  determined. 

1  Hawaii  Sta.  Press  Bui.  23;  Jour.  Indus,  and  Engin.  Chem.,  1   (1909),  pp.  533-538. 

2  Hawaii  Sta.  Rpt.   1909,  p.   63. 

[Bull.  28] 


13 


THE     COMPOSITION     OF     THE     PINEAPPLE     PLANT     AS     AFFECTED     BY 

MANGANESE. 

Ill  this  investigation  a  number  of  representative  plants  from 
highly  manganiferous  soil,  on  the  one  hand,  and  from  normal  soil, 
on  the  other,  were  separated  into  leaves  and  stalk,  and  after  becom- 
ing thoroughly  air  dried  were  subjected  to  analysis.  The  ash  was 
determined  by  incinerating  over  a  free  flame  at  a  temperature  well 
below  redness,  then  leaching  with  distilled  water,  according  to  the 
optional  method  of  the  Association  of  Official  Agricultural  Chemists 
for  the  determination  of  ash  in  plants.1  The  several  mineral  con- 
stituents were  determined  in  samples  of  the  ash  thus  obtained.  It 
should  be  mentioned  in  this  connection  that  the  percentages  of  sul- 
phur, chlorin,  and  possibly  phosphorus  pentoxid,  should  not  be  con- 
sidered as  absolute,  for  the  reason  that  partial  volatilization  may 
have  taken  place.  In  the  case  of  phosphorus  pentoxid,  a  number  of 
determinations  were  made  by  the  use  of  wet  methods,  and  results 
closely  agreeing  with  those  secured  from  the  ash  were  obtained,  so 
that  fair  accuracy  is  believed  to  have  been  obtained.  In  any  event, 
the  results  are  comparable  among  themselves,  and  since  it  is  for  this 
purpose  that  they  are  submitted,  their  value  is  not  greatly  impaired. 

The  composition  of  the  ash  of  leaves  and  stalk  from  the  two  classes 
of  soil  is  recorded  in  the  following  table : 2 

Composition  of  pineapple  leaves  and  stalk. 


Leaves. 


Stalk. 


5  months 
old  from 
manganif- 
erous soil. 


5  months 

old  from 

normal 

soil. 

18  months 
old  from 
manganif- 
erous soil. 

18  months 

old  from 

normal 

soil. 

5  months 
old  from 
manganif- 
erous soil. 

5  months 

old  from 

normal 

soil. 

18  months 
old  from 
manganif- 
erous soil. 

Per  cent. 
7.14 

Per  cent. 
7.98 

Per  cent. 
6.24 

Per  cent. 
8.86 

Per  cent. 
5.12 

Per  cent. 
7.78 

8.49 
1.20 

5.72 
1.76 

7.36 
.40 

5.20 
.40 

2.27 
1.56 

1.72 
4.52 

1.11 

.96 

.48 

.60 

.70 

Trace. 

1.70 
7.14 
7.60 
22.97 
16.72 

2.08 
15.66 

7.91 
18.86 
14.35 

1.40 

7.00 

6.98 

22.86 

17.12 

.25 
36.42 

2.60 
16.79 

2.65 

.25 
23.87 

5.82 
24.18 

1.65 

.20 
14.36 

7.75 
32.26 

1.10 

3.57 

1.66 

2.70 

6.12 

8.86 

6.70 

2.72 
13.33 

2.70 
13.61 

3.85 
8.86 

20.99 
6.31 

16.36 
9.36 

16.81 
11.13 

18  months 

old  from 

normal 

soil. 


Per  cent. 

Ash I         9.94 

Ash.  constituents:        L 

Silica  (Si02) 9.37 

Alumina  (A1203) .  2. 12 

Ferric    oxid 

(Fe203) 81 

Manganese   oxid 

(M113O4) 2.41 

Lime(CaO) 9.01 

Magnesia  (MgO).  5.70 

Potash  (K20)....  21.09 

Soda(Na20) 19.48 

Phosphorus  pen- 
toxid (P205)...  2.81 
Sulphur    trioxid 

(S03) 2.62 

Chlorin  (CI) 13.37 


Per  cent. 
6.60 


2.84 
6.02 


Trace. 


12.96 

5.78 

33.01 

.60 

8.36 

22.93 
8.01 


These  data  show  that  there  is  a  wide  range  of  variation  in  the  inor- 
ganic constituents  of  the  plant.     Considerable  differences  have  been 


1U.  S.  Dept.  Agr.,  Dur.  Chem.  Bui.  107   (rev.),  p.  238. 

'Analyses  of  the  roots  were  not  made,  for  the  reason  that  it  is  very  difficult  to  remove 
all  traces  of  adhering  soil  from  pineapple  roots  when  grown  in  Hawaii. 
[Bull.  28] 


14 

observed  in  the  percentages  of  the  mineral  elements  in  a  given  species 
of  plant  when  grown  under  different  environments,  such  as  are 
afforded  by  different  types  of  soil,  climatic  variations  and  lati- 
tudinal changes,  and  the  exact  significance  of  the  variations  thus 
induced  isnot  fully  understood;  but  the  variations  in  the  compo- 
sition of  pineapple  ash,  herein  reported,  especially  as  regards  the 
lime,  magnesia,  and  phosphorus  pentoxid,  are  believed  to  have  spe- 
cial importance.  The  significance  of  these  data  has  been  fully  inter- 
preted in  a  previous  publication  which  is  devoted  to  a  comprehensive 
study  of  the  function  of  manganese  in  plant  growth.1 

At  this  time  it  is  wished  merely  to  call  attention  to  the  excessive 
amounts  of  lime  and  the  relatively  smaller  amounts  of  magnesia,  as 
well  as  a  correspondingly  smaller  percentage  of  phosphorus  pentoxid, 
in  the  plants  from  manganiferous  soils.  As  previously  mentioned, 
the  occurrence  of  calcium  oxalate  crystals  is  much  more  abundant  in 
the  chlorotic  plants;  in  fact  the  presence  of  calcium  oxalate  forms 
one  of  the  noticeable  characteristics  in  all  parts  of  these  plants ;  and 
while  this  so-called  by-product  occurs  in  considerable  amounts  in 
normal  pineapple  plants,  the  amount  is  in  great  excess  in  the  chlo- 
rotic plants.  Various  authorities  have  discussed  the  occurrence  of 
calcium  oxalate  in  plants,  and  in  general  they  are  agreed  that  one  of 
the  functions  of  lime  in  plants  is  to  neutralize  the  acids  formed  as 
a  result  of  metabolism.  One  of  the  principal  acids  thus  formed  is 
oxalic,  which  has  been  supposed,  by  various  authorities,  to  result  from 
at  least  two  different  sources:  (1)  It  may  arise  from  a  decomposition 
of  carbohydrates  during  plant  respiration;  and  (2)  it  is  thought  to 
be  derived,  in  some  instances,  from  the  breaking  up  of  protoplasm.   - 

In  chlorotic  pineapples  there  have  been  observed  a  general  disin- 
tegration and  breaking  up  of  the  organized  structure  of  the  proto- 
plasm and  the  complete  disappearance  of  the  chloroplasts.  With 
this  there  is  a  simultaneous  appearance  of  oxalate  of  calcium.  From 
these  observations  the  conclusion  may  be  drawn  that  the  excessive 
amount  of  oxalic  acid  in  chlorotic  pineapples  results  from  a  decom- 
position of  the  protoplasm  itself,  and  that  its  neutralization  and  sub- 
sequent crystallization  is  made  possible  through  the  presence  of 
abnormal  amounts  of  lime  in  the  cell  sap. 

THE  RIPENING  OF  THE  PINEAPPLE  FRUIT. 

As  has  been  clearly  shown  by  numerous  chemical  analyses  made  at 
this  station,  it  is  a  peculiar  feature  of  the  ripening  of  the  pineapple 
fruit  that  no  increase  in  the  amount  of  sugar  takes  place  during  the 
ripening  process  if  the  fruit  has  been  removed  from  the  plant.  It 
is  apparent,  therefore,  that  the  materials  which  are  transformed  into 
sugar  are  to  be  sought  in  other  parts  of  the  plant  than  the  fruit. 

i  Hawaii  Sta.  Bui.  26. 
[Bull.  28] 


15 

Sections  were  made  through  all  parts  of  the  pineapple  plant  from  the 
base  of  the  stem  to  the  crown  with  the  result  that  the  distribution  of 
starch  is  found  to  be  strictly  in  harmony  with  the  chemical  findings 
of  the  ripening  of  the  fruit.  In  the  dead  and  partially  decomposed 
basal  end  of  the  stem  there  is  relatively  little  starch,  and  that  which 
is  present  is  for  the  most  part  removed  some  distance  from  the  fibre- 
vascular  tissue.  The  parenchyma  cells  in  the  stem,  with  the  except  ion 
of  the  dead  base,  are  completely  filled  with  starch ;  in  fact,  these  trunks 
apparently  contain  as  high  a  percentage  of  starch  as  potatoes  or  other 
plant  structures  used  in  the  commercial  manufacture  of  starch.  The 
station  has  planned  some  experiments  to  show  whether  old  pineapple 
stumps  which  have  heretofore  been  thrown  away  may  be  used  com- 
mercially for  obtaining  starch.  The  storage  of  starch  continue- 
upward  to  the  attachment  of  the  uppermost  regular  leaves,  where  it 
suddenly  ceases.  As  sections  are  made  in  the  fruit  stem  above  this 
point,  it  is  found  that  starch  is  almost  entirely  absent  up  to  the  point 
where  the  small  bracts  are  attached  to  the  base  of  the  fruit.  Here, 
especially  in  normal  plants,  the  accumulation  of  starch  is  quite  con- 
spicuous. 

In  the  very  young  fruit  at  flowering  time  small  granules  of  starch 
may  be  found  at  the  base  of  the  bra-cts  under  each  eye  and  occasionally 
throughout  the  substance  of  the  fruit.  At  the  base  of  the  crown 
leaves  there  is  a  considerable  accumulation  of  starch  and  a  few  gran- 
ules are  found  in  the  core.  The  crown  in  young  fruits  contains  a 
large  quantity  of  starch. 

It  is  a  peculiar  fact  that  old  stumps  connected  only  by  means  of 
a  dead  stem  with  ratoon  stems  contain  fully  as  much  starch  as  the 
latter.  The  old  stumps  are  known  to  be  capable  of  producing  pine- 
apple plants  and  have  been  especially  recommended  for  highly  man- 
ganiferous  soils.  It  is  likely  that  in  such  cases  the  plants  are  able 
to  develop  from  the  large  supply  of  starch  found  in  the  stems. 
Starch  is  quite  abundant  throughout  the  length  of  all  normal  leaves. 
When  the  fruit  is  about  half  grown  it  contains  only  an  occasional 
starch  grain  here  and  there  just  underneath  the  green  epidermis. 
In  ripe  fruit  it  is  almost  impossible  to  find  even  a  trace  of  starch 
in  any  part  of  the  fruit.  It  is  evident  from  this  distribution  of 
starch  that  the  source  of  material  to  be  modified  by  hydrolysis  into 
sugar  is  almost  exclusively  outside  of  the  fruit.  The  few  granules 
of  starch  found  under  the  green  epidermis  of  unripe  fruit  and  the 
small  quantity  of  starch  in  the  crown  are  insufficient  to  make  any 
practical  addition  to  the  sugar  content  of  pineapples  which  are 
allowed  to  ripen  after  removal  from  the  plant-. 

In  this  connection  it  is  interesting  to  note  the  fad  that  some  pine- 
apple grower-  consider  the  crown  as  a  parasite  of  the  fruit  or  as 

[Bull.  28] 


16 

growing  at  the  expense  of  the  fruit.  Experiments  in  removing  the 
crown  from  young  fruits  indicate  that  the  core  is  thereby  rendered 
smaller  and  that  the  fruit  is  larger  in  cross  diameter  at  the  top,  as- 
suming a  more  cylindrical  shape.  The  facts  which  have  been  stated 
regarding  the  distribution  of  starch  in  the  pineapple  plant  and 
therefore  of  the  possible  sources  of  sugar  in  the  ripening  of  pine- 
apple fruits  are  in  harmony  with  the  findings  of  Hume  and  Miller,1 
that  the  sugar  content  is  higher  at  the  base  of  the  fruit  than  in  the 
crown  and  higher  nearer  the  core  than  at  the  surface.  This  would 
indicate  that  the  sugar  enters  the  fruit  through  the  fruit  stem  at  the 
base. 

While  pineapples  in  ripening  after  removal  from  the  plant  do  not 
develop  any  higher  sugar  content  than  they  had  at  the  time  of  re- 
moval, they  nevertheless  undergo  all  the  other  processes  which  are 
characteristic  of  ripening.  The  color  changes  are  the  same  as  those  in 
fruits  which  ripen  on  the  plant  and  the  fruit  becomes  soft  and  juicy. 
It  is  a  matter  of  common  knowledge  that  only  a  small  amount  of 
juice  runs  out  of  the  cut  surface  of  a  green  pineapple  while  much 
larger  quantities  escape  from  similar  cuts  from  ripe  pineapples.  This 
is  at  least  partly  explained  by  reference  to  D  and  E  of  Plate  II.  In 
D  is  seen  a  cell  from  the  soft  pulp  of  a  completely  ripened  pineapple. 
The  cell  wall  is  thin,  delicate,  and  is  easily  torn.  In  fact  the  walls 
here  and  there  in  ripe  fruits  are  completely  broken  down  in  the 
ripening  process  so  that  some  of  the  larger  cavities  may  be  parts  of 
what  was  previously  several  cells.  In  the  green  fruits,  on  the  other 
hand,  as  shown  in  E,  Plate  II,  the  cell  walls  of  the  pulp  tissue  of  the 
fruit  are  much  thicker.  The  thickening  of  these  cell  walls  is  com-" 
posed  of  irregular  masses  of  a  collagenous  nature.  During  the  ripen- 
ing process  this  material  appears  to  be  dissolved,  leaving  the  thin  cell 
wall  of  the  delicate  tissue  which  is  characteristic  of  the  pulp  of  ripe 
fruit. 

THE  CHEMISTRY  OF  RIPENING. 

The  physiology  of  the  pineapple  plant  indicates  some  peculiarities 
belonging  to  this  plant,  and  which  are  different  from  those  of  most, 
fruits.  The  chemical  changes  taking  place  during  ripening  have 
previously  received  some  attention  at  this  station,2  and  in  order  to 
have  a  more  strict  chemical  basis  for  the  interpretation  of  the  physi- 
ology already  outlined,  it  is  thought  that  a  further  discussion  of  these 
data  will  be  of  interest.  It  has  been  shown  that  the  average  composi- 
tion of  the  green  fruit,  just  before  the  beginning  of  the  ripening 
process,  is  as  follows :  Acidity,  as  sulphuric  acid,  0.39  per  cent ;  fiber, 

1  Florida  Sta.   Bui.   70. 

2IIaw;iii  Sta.  Rpt.  1910,  pp.  45-50;  Jour.  Indus,  and  Engin.  Chem.,  3  (1911),  pp. 
403-40.1. 

[Bull.  28] 


17 

0.17  per  cent;  solids  in  the  juice,  G.89  per  cent;  total  hydrolyzable 
carbohydrates,  expressed  as  invert  sugar,  5.80  per  cent ;  reducing 
sugars,  as  invert  sugar,  3.29  per  cent;  sucrose,  1.72  per  cent;  and 
total  sugars,  5.01  per  cent. 

The  point  of  special  interest  in  these  data  is  the  small  percentage 
of  sugars  in  the  green  fruit.  It  should  be  borne  in  mind  in  this  con- 
nection that  the  above  data  were  secured  from  fully  grown  fruit 
which,  so  far  as  could  be  judged,  were  just  at  the  beginning  of  the 
ripening  process.  In  addition,  these  analyses  were  made  by  the  use 
of  the  fruit  itself,  rather  than  the  juice.  While  the  reducing  sugars 
and  sucrose  make  up  a  small  percentage  of  total  sugars  the  hydro- 
lyzable carbohydrates,  which  were  determined  by  boiling  samples 
of  the  fruit  with  hydrochloric  acid,  show  that  the  storage  of  reserve 
material  in  the  growing  pineapple  is  slight,  and  if  severed  from  the 
plant  at  this  stage  it  can  not  possibly  develop  a  normal  sugar  con- 
tent in  subsequent  ripening.  Pineapples  gathered  green  and  allowed 
to  ripen  afterwards  were  found  to  have  the  following  average  com- 
position: Acidity,  0.58  per  cent;  fiber,  0.22  per  cent;  solids  in  the 
juice,  6.45  per  cent;  reducing  sugars,  1.22  per  cent;  sucrose,  3.90 
per  cent;  total  sugars,  4.12  per  cent;  and  total  hydrolyzable  carbo- 
hydrates, as  invert  sugar,  4.35  per  cent. 

The  principal  changes  that  take  place  in  this  process  are  the  con- 
version of  reducing  sugars  into  sucrose,  and  a  slight  increase  in 
acidity.  There  is  a  pronounced  development  of  flavor  and  a  general 
softening  of  the  tissues,  but  the  true  fiber  is  not  materially  changed. 
The  average  composition,  when  approximately  one-fourth  ripe,  was 
found  to  be  as  follows:  Acidity,  0.65  per  cent;  solids  in  the  juice, 
8.68  per  cent;  reducing  sugars,  2.74  per  cent;  sucrose,  4.42  per  cent; 
total  sugars,  7.16  per  cent;  and  when  half  ripe  the  fruit  contains: 
Acidity,  0.65  per  cent;  reducing  sugars,  2.97  per  cent;  sucrose,  6.74 
per  cent ;  and  total  sugars,  9.71  per  cent.  When  allowed  to  ripen  nor- 
mally on  the  plant,  the  composition  was  found  to  be  as  follows: 
Acidity,  0.74  per  cent;  reducing  sugars,  4.23  per  cent;  sucrose,  7.88 
per  cent ;  and  total  sugars,  12.11  per  cent 

The  composition  at  the  several  stages  of  ripening  shows  that  there 
is  a  rapid  accumulation  of  sugars,  especially  sucrose,  and  a  slight  in- 
crease in  acidity  during  the  development  of  the  fruit.  From  a  study 
of  the  physiology  of  this  plant  we  can  better  understand  the  analytical 
data.  It  has  been  shown  that  the  normal  pineapple  plant  stores  up 
large  amounts  of  starch  in  the  stalk  and  base  of  the  leaves,  whereas 
only  faint  traces  of  starch  could  be  detected  in  any  portion  of  the 
fruit  at  any  stage  of  its  development.  The  fruit  stem  was  found  to 
contain  small  quantities  of  starch ;  also  there  are  scattering  granules 
in  the  cells  immediately  adjacent  to  the  epidermis.    These  cells  were 

[Bull.  28] 


18 

also  found  to  contain  a  small  amount  of  starch  adhering  to  the  chloro- 
plastids.  The  deeper- lying  tissues  rarely  contain  any  starch ;  neither 
was  dextrin  detected  in  more  than  mere  traces;  and  from  the  results 
of  acid  hydrolysis  we  may  conclude  that  the  green  fruit  contains  no 
substance  of  importance  that  is  capable  of  giving  rise  to  sugars  during 
subsequent  ripening. 

The  chief  carbohydrates  produced  in  the  plant,  then,  may  be  con- 
sidered to  be  of  the  nature  of  sugars  and  starch,  and  these  may  be" 
looked  upon  as  being  produced  somewhat  as  follows :  The  protoplasm 
transforms  carbon  dioxid  and  water  into  sugars  by  the  intervention 
of  chlorophyll,  just  as  is  done  in  all  plants.  The  excessive  accumula- 
tion of  sugar  in  the  chlorophyll-bearing  cells  is  prevented  by  its 
transformation  into  starch,  which,  in  turn,  is  stored  principally  in 
the  stalk.  During  the  vegetative  growth  of  the  fruit  relatively  small 
amounts  of  carbohydrates  are  transferred  to  it,  but  in  the  normal 
ripening  process  there  is  an  enormous  accumulation  of  sugars  in  the 
fruit,  which  sugars  are  derived  from  the  carbohydrates  previously 
stored  as  starch  in  the  stem. 

Normally,  pineapples  stand  almost  perpendicular  and  are  some- 
what protected  from  the  direct  rays  of  the  sun  by  the  crown.  Occa- 
sionally there  are  to  be  observed  in  the  fields  pineapples  that  have 
weak  steins,  which  results  in  the  fruit  becoming  turned  over  and 
exposing  one  side  to  the  direct  rays  of  the  sun.  The  pineapples 
that  are  thus  exposed  become  blanched  on  the  upper  side,  which  ap- 
pears to  mature  earlier  than  the  lower  and  more  protected  surface. 
Such  pineapples  also  are  less  palatable  in  the  upper  and  exposed 
portion. 

With  a  view  of  determining  the  composition  of  such  fruits  a  num- 
ber of  analyses  have  been  made.  These  pineapples  were  sampled  in 
such  way  as  to  secure  one  portion  from  the  upper  side  and  one  from 
the  lower  side.  Partial  analyses  of  these  portions  are  recorded  as 
follows : 

The  composition  of  upper  and  lower  portions  of  pineapples. 


Serial 
No. 

Acidity 
asH2S04. 

Reducing 

sugars 

calculated 

as  invert 

sugar. 

Sucrose. 

Total 
sugars. 

Polarization. 

Direct. 

Invert. 

Tempera- 
ture. 

119 

Per  cent. 
0.51 
.51 
.40 
.74 
.88 
.98 
.72 
.55 
.63 
.69 

Per  cent. 
3.06 
4.35 
4.00 
3.44 
3.33 
2.98 
4.17 
4.54 
3.64 
3.83 

Per  cent. 
5.58 
8.42 
4.81 
6.17 
6.78 
8.41 
7.48 
8.45 
6.16 
7.86 

Per  cent. 

8.64 
12.77 

8.81 

9.61 
10.11 
11.39 
11.65 
12.99 

9.80 
11.69 

4.1 
6.4 
3.4 
4.7 
4.9 
6.4 
5.6 
6.3 

°V. 

-3.0 
-4.3 
-2.8 
-3.1 
-3.7 
-4.3 
-4.0 
-4.5 

°C. 
31.0 

119 

31.4 

120 

31.7 

120 

32.5 

121 

31.7 

121 

30.8 

122 

28.6 

122 

Lcwer  side 

29.7 

Average,  upper  side. . . 
Average,  lower  side . . . 

[Bull.  28] 


19 

These  data  show  that  a  considerably  greater  amount  of  sucrose  w 
deposited  in  the  lower  and  more  protected  portion  of  the  fruit.  This 
may  be  partially  accounted  for  by  the  fact  that  the  ripening  process 
is  abnormal  in  character  and  more  hastened  in  the  blanched  portion 
of  the  fruit.  There  seems  to  be  no  evidence  for  believing  that  the 
hydrolysis  of  starch  in  the  stalk  and  the  diffusing  of  sugars  to  the 
fruit  continues  after  the  fruit  becomes  thoroughly  ripe,  even  if  it 
be  left  attached  to  the  plant.  The  period  of  transference  of  sugars 
to  the  blanched  portion  of  such  pineapples,  therefore,  is  shorter  and 
consequently  it  should  contain  less  sugars.  In  addition,  osmosis  may 
in  some  way  be  modified  by  the  effects  of  direct  rays  of  the  sun  on 
the  fruit. 

SUMMARY. 

The  root  system  of  pineapples  is  very  variable  and  particularly 
sensitive  to  adverse  soil  conditions.  When  grown  in  manganiferous 
soil  the  roots  are  less  extensive  and  the  ends  of  the  roots  are  charac- 
terized by  the  development  of  swollen  tips,  the  appearance  of  which 
seems  to  mark  the  cessation  of  the  lateral  growth  of  the  roots,  death 
and  decay  immediately  following  their  development.  The  cells  im- 
mediately beneath  the  epidermis  of  the  roots  are  also  somewhat  more 
brown  than  are  normal  roots. 

The  stem  of  pineapples  serves  as  a  repository  for  starch  and  con- 
tains large  amounts  of  this  substance. 

The  leaves  of  pineapples  in  common  with  other  members  of  Brome- 
liaceaa  contain  several  rows  of  palisade  cells  which  contain  nothing 
but  cell  sap,  and  the  chlorophyll  is  confined  to  the  spongy  paren- 
chyma in  the  lower  three-fifths  of  the  leaf.  The  fruit  contains  only 
faint  traces  of  starch  during  early  growth  and  when  it  reaches 
maturity  starch  is  absent  from  it. 

The  most  conspicuous  effect  of  manganese  on  this  plant  is  seen  in 
the  bleaching  of  the  chlorophyll  which  first  begins  to  fade,  the 
chloroplasts  lose  their  organized  structure,  and  later  the  color  dis- 
appears altogether.  Oxalate  of  calcium  is  much  more  abundant  in 
pineapple  plants  growing  on  manganiferous  soils.  The  ash  of  such 
plants  also  contains  considerably  more  lime  and  less  phosphorus 
pentoxid  and  magnesia  than  when  grown  on  normal  soils. 

During  the  growth  of  the  fruit  relatively  small  amounts  of  sugars 
are  stored  in  it,  but  within  the  short  period  of  normal  ripening  there 
is  a  rapid  accumulation  of  sugars  in  the  fruit.  Pineapples  gathered 
green  do  not  develop  a  normal  sugar  content  in  subsequent  ripening. 
The  sugars  of  the  fruit  are  derived  from  the  starch  previously  stored 
in  the  stalk. 

[Bull.  28] 


20 

The  study  of  the  pineapple  shows  that  it  is  exceedingly  sensitive  to 
adverse  physical  and  chemical  conditions  in  the  soil.  So  far  as  is 
known  at  present,  there  is  no  really  satisfactory  program  by  which 
pineapples  can  be  grown  on  highly  manganiferous  soils.  It  seems 
best  to  use  such  areas  for  other  crops  less  sensitive  to  manganese. 
The  best  method  of  handling  pineapples  on  manganiferous  soils  con- 
sists in  applying  soluble  phosphates  and  planting  old  stumps  instead 
of  suckers. 

[Bull.  28] 


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